Dual Bore Packer with Axially Offset Mandrel Threads

ABSTRACT

A dual bore packer features axially offset tapered thread connections so that the pressure rating and size of the connections in each of the bores can be as large as possible. This is enabled by providing as thick a wall as possible between the bores in the zone where the connecting tapered thread is placed.

FIELD OF THE INVENTION

The field of the invention is dual bore packers and more particularlypackers where the mandrel end connections are axially offset to allowgreater wall area about the thread for the required pressure rating.

BACKGROUND OF THE INVENTION

Typically dual bore packers have two adjacent bores with threaded endconnections for connecting a tubular string or a cable. One applicationfor dual bore packers is for electric submersible pump service where thesmaller of the bores is for a power cable to the pump and the largerbore is connected to the discharge of the pump to bring produced fluidsto the surface. Some examples of dual bore packers with axially alignedthreads are U.S. Pat. No. 9,611,722 and U.S. Pat. No. 6,390,198.

Typically the threaded connections have to deliver a required pressurerating and if the threads are disposed next to each other at the upperface of the mandrel there has to be a tradeoff between making the threadas large as possible for less resistance to flow and making theconnections stout enough to handle the anticipated operating pressuresfor the application. Since the thread forms are tapered juxtaposing twothreads near each other limits the available wall between them so as toreduce the pressure rating of the connections. In dual bore packers thecenter of each bore is offset from the center of the packer.

The present invention offers a simple solution to this design conflictbetween making the bores as large as possible and giving the connectionsthe highest possible pressure rating. The solution is to axially offsetthe threads in adjacent bores to maximize the available surrounding wallthickness so that in a given packer mandrel size the diameter andpressure rating of the two bores is maximized. These and other aspectsof the present invention will be more readily apparent to those skilledin the art from a description of the preferred embodiment and theassociated drawings while recognizing that the full scope of theinvention can be determined from the appended claims.

SUMMARY OF THE INVENTION

A dual bore packer features axially offset tapered thread connections sothat the pressure rating and size of the connections in each of thebores can be as large as possible. This is enabled by providing as thicka wall as possible between the bores in the zone where the connectingtapered thread is placed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section view of a dual bore packer showing the offset threadlocations in adjacent bores;

FIG. 2 is an end view of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A mandrel end 10 of a dual bore packer of a type known in the art isshown in FIG. 1. First bore 12 is disposed parallel to second bore 14.In one application bore 12 is larger than bore 14 such as inapplications for an electric submersible pump where the productiondischarge line from the pump is connected to bore 12 and a power cablegoes through bore 14. Typically the bores 12 and 14 have their centersoffset from the center of the mandrel 10. Bore 12 has a threadedconnection 16 axially offset and preferably not overlapping from thread18 in bore 14. In the case of more bores than two it is preferred thateach connection be at least offset if not non-overlapping from all theother connections on the mandrel. Because thread 18 is tapered, theresult is the wall 20 between the bores 12 and 14 gets thinner. The sameis true for thread 16 at wall portion 22. However, because threads 16and 18 are axially offset and preferably non-overlapping in the axialdirection there is no need to reduce the pressure rating of eitherthreaded connection because placement of the thread takes away some ofthe wall. Instead the available wall thickness at each thread locationis as large as possible availing a higher pressure rating to theconnection than if the two threads were axially aligned or even if theywere only in part axially overlapping. While tapered threads arediscussed as the end connections, those skilled in the art willappreciate that other types of connections are envisioned whetherthreaded, socket welded, bayonet or another form of connection.

The above description is illustrative of the preferred embodiment andmany modifications may be made by those skilled in the art withoutdeparting from the invention whose scope is to be determined from theliteral and equivalent scope of the claims below:

1. A connection arrangement for a multi-bore packer for borehole use,comprising: a mandrel having multiple bores coextensive from a commontop to a common bottom end of said mandrel, each said bore having aconnection within said mandrel wherein said connections within saidbores are axially offset from each other.
 2. The connection arrangementof claim 1, wherein: said connections do not axially overlap.
 3. Theconnection arrangement of claim 2, wherein: said connections comprisetapered thread.
 4. The connection arrangement of claim 2, wherein: atleast one said connection starts at an end of said mandrel.
 5. Theconnection arrangement of claim 2, wherein: said bores are differentsizes.
 6. The connection arrangement of claim 2, wherein: said boreshave centers offset from a center of said mandrel.
 7. The connectionarrangement of claim 2, further comprising: a power cable for anelectric submersible pump connected to one of said bores and a tubularstring connected to another of said bores to direct flow from said pumpto a remote location.
 8. The connection arrangement of claim 1, wherein:said mandrel comprises two said bores.